Is the Live API's rejection of enum in function schemas a known limitation?

[XinyueZ]

Steps to Reproduce

1. Create a LlmAgent with a Gemini Live model.
2. Pass a sub-agent via sub_agents=[some_agent] (mode defaults to chat).
3. Start a Live session → WebSocket connection fails with HTTP 503.
4. Move the same agent to tools=[AgentTool(agent=some_agent)] → works correctly.

Questions

• Is the Live API's rejection of enum in function schemas a known limitation?
• Is AgentTool the officially recommended pattern for sub-agents when the parent uses the Live API?
• Should ADK detect a Live API model and skip/adapt TransferToAgentTool schema generation accordingly?

Environment

• google-adk (latest)
• Parent model: Gemini Live API (native audio)
• Sub-agent model: standard (non-live) Gemini model

[boyangsvl]

/adk-issue-analyze

[llalitkumarrr]

Hello @XinyueZ ,

Could you please share your ADK version so we can try to reproduce this issue?

Additionally we recommend using a non-live Gemini model agent as a tool (i.e AgentTool). However for testing purposes, could you try using the live Gemini model as a sub agent to see if that works? Kindly let us know your findings.

[XinyueZ]

The latest version.
The issue occurs if we use it as sub.
If as tool, no problem.

I just want to know, and confirm from official developer.

[llalitkumarrr]

Yes, using non-live models as sub agents can cause this issue. Therefore we recommend configuring them as AgentTools instead.